This invention relates to semiconductor fabrication processing and more particularly, to methods for forming programmable capacitor dynamic random access memories (PCRAMs) utilizing a programmable metallization cell.
Memory devices are used in electronic systems and computers to store information in the form of binary data. These memory devices may be characterized as either volatile memory, where the stored data is lost if the power source is disconnected or removed or non-volatile, where the stored data is retained even during power interruption. An example of a non-volatile memory device is the programmable conductor random access memory (PCRAM) that utilizes a programmable metallization cell (PMC).
A PMC comprises a fast ion conductor such as a chalcogenide-metal ion and at least two electrodes (e.g., an anode and a cathode) comprising an electrically conducting material and disposed at the surface of the fast ion conductor a set distance apart from each other. When a voltage is applied to the anode and the cathode, a non-volatile metal dendrite rapidly grows from the cathode along the surface of the fast ion conductor towards the anode.
The growth rate of the dendrite is a function of the applied voltage and time; the growth of the dendrite may be stopped by removing the voltage or the dendrite may be retracted back towards the cathode, or even disintegrated, by reversing the voltage polarity at the anode and cathode. Changes in the length and width of the dendrite affect the resistance and capacitance of the PMC.
One of the important elements of the PMC is the fast ion conductor, which plays a critical part during the programming of the PMC. The construction of the fast ion conductor is key to providing effective and reliable programming of the PMC and is a significant focus of the present invention.
Thus, the present invention comprises fabrication techniques to form a programmable metallization cell, for use in a programmable conductor random access memory, that will become apparent to those skilled in the art from the following disclosure.
An exemplary embodiment of the present invention includes a method for forming a programmable cell by forming an opening in a section of a dielectric material to expose a portion of an underlying first conductive electrode forming a recessed chalcogenide-metal ion material in the opening; and forming a second conductive electrode overlying the dielectric material and the chalcogenide-metal material.
A method for forming the recessed chalcogenide-metal ion material comprises forming a metal material being recessed approximately 10-90%, in the opening in the dielectric material, forming a glass material on the metal material and diffusing metal ions from the metal material into the glass material by using ultraviolet light or ultraviolet light in combination with a heat treatment, to cause a resultant metal ion concentration in the glass material.